It is proposed to display a television picture by using, for example, a liquid crystal.
In FIG. 11, reference numeral 1 designates an input terminal to which a television video signal is supplied. The signal from this input terminal 1 is supplied through switching elements M.sub.1, M.sub.2, . . . M.sub.m, each of which is formed of, for example, an N-channel FET, to lines L.sub.1, L.sub.2, . . . L.sub.m in the vertical (Y axis) direction where m is the number corresponding to the number of the picture elements in the horizontal (X axis) direction. Further, there is provided a shift register 2 having m stages. This shift register 2 is supplied with clock signals .phi..sub.1H, .phi..sub.2H each having a frequency m times the horizontal frequency. Drive pulse signals .phi..sub.H1, .phi..sub.H2, . . . .phi..sub.Hm, which are derived from the respective output terminals of this shift register 2 and sequentially scanned by the clock signals .phi..sub.1H, .phi..sub.2H, are supplied to the respective control terminals of the switching elements M.sub.1 to M.sub.m. To the shift register 2, there are supplied a low potential (V.sub.SS) and a high potential (V.sub.DD) and thereby drive pulses of two potentials are generated.
To the respective lines L.sub.1 to L.sub.m, there are connected one ends of switching elements M.sub.11, M.sub.21, . . . M.sub.nl, M.sub.12, M.sub.22, . . . M.sub.n2, . . . M.sub.lm, M.sub.2m, . . . M.sub.nm, which are each formed of, for example, an N-channel FET, where n is the number corresponding to the number of the horizontal scanning lines. The other ends of these switching elements M.sub.11 to M.sub.nm are respectively connected through liquid crystal cells C.sub.11, C.sub.21, . . . C.sub.nm to a target terminal 3.
Further, there is provided a shift register 4 having n stages. This shift register 4 is supplied with clock signals .phi..sub.1V and .phi..sub.2V each having a horizontal frequency. Drive pulse signals .phi..sub.V1, .phi..sub.V2, . . . .phi..sub.Vn, which are derived from the respective output terminals of this shift register 4 and sequentially scanned by the clock signals .phi..sub.1V and .phi..sub.2V, are supplied through gate lines G.sub.1, G.sub.2, . . . G.sub.n in the horizontal (X axis) directions to control terminals of the switching elements M.sub.11 to M.sub.nm at every rows (M.sub.11 to M.sub.1m), (M.sub.21 to M.sub.2m), . . . (M.sub.n1 to M.sub.nm) in the X axis direction, respectively. Also, the shift register 4 is supplied with the potentials V.sub.SS and V.sub.DD similarly to the shift register 2.
That is, in this circuit, to the shift registers 2 and 4, there are supplied the clock signals .phi..sub.1H, .phi..sub.2H, .phi..sub.1V and .phi..sub.2V which are shown in FIGS. 12A and 12B. Then, the shift register 2 generates signals .phi..sub.H1 to .phi..sub.Hm at every picture element periods as shown in FIG. 12C, while the shift register 4 generates signals .phi..sub.V1 to .phi..sub.Vn at every one horizontal period as shown in FIG. 12D. Further, to the input terminal 1, there is supplied a signal as shown in FIG. 12E.
When the signals .phi..sub.V1 and .phi..sub.H1 are generated, the switching elements M.sub.1 and M.sub.11 to M.sub.1m are turned on and thereby a current path from the input terminal 1 through M.sub.1, L.sub.1, M.sub.11, C.sub.11 to the target terminal 3 is formed, through which a potential difference between the signal supplied to the input terminal 1 and the signal at the target terminal 3 is supplied to the liquid crystal cell C.sub.1 l. As a result, in the capacity portion of the cell C.sub.11, there is sampled and then held a charge corresponding to a potential difference made by the signal of a first picture element. The optical transmissivity of the liquid crystal is changed in response to this charge amount. The similar operation is sequentially carried out on the following cells C.sub.12 to C.sub.nm. Further, when the signal of the next field is supplied, the charge amounts of the respective cells C.sub.11 to C.sub.nm are re-written.
As described above, the optical transmissivities of the liquid crystal cells C.sub.11 to C.sub.nm are changed in response to the respective picture elements of the video signal, and this operation is sequentially repeated to thereby display a television picture.
By the way, when the display is made by the liquid crystal, an AC drive system is generally adopted so as to improve its reliability and its service life. For example, in the display of a television picture, a signal, which results from inverting a video signal at every one field or at every one frame, is supplied to the input terminal 1. In other words, to the input terminal 1, there is supplied a signal which is inverted at every one field or at every one frame as shown in FIG. 12E.
By the way, in the above mentioned apparatus, picture element electrodes P of the respective liquid crystal cells C are aligned in the vertical and horizontal directions as shown by broken lines in the figure. On the other hand, when the television picture is displayed, in order to miniaturize the circuit scale, two pictures provided by a so-called interlace are displayed on the same display section. For this reason, the prior art apparatus has a problem that the vertical resolution is lowered.
That is, as shown, for example, in FIG. 13A, when a black color is displayed on an n-th scanning line of a first interlaced field and on an n+264th scanning line of a second interlaced field and a white picture is displayed on other scanning lines, if they are displayed on the same display section, the black and white pictures are alternately displayed on adjacent two display sections as shown in FIG. 13B. One square in the figure represents one liquid crystal cell, a character on the upper side thereof represents the display of black color (B) and white color (W) on the first field and a character on the lower side thereof represents those displayed on the second field. As will be clear from this figure, when the above mentioned picture is displayed, the display is made such that one grey line having a double width is displayed on the whole and thus the vertical resolution is lowered.
Further in the afore-mentioned apparatus, if color filters having different colors are disposed at every liquid crystal cells C and the video signals applied to the input terminal 1 are made as corresponding color signals, it is possible to make the color display. In that case, the picture element electrodes P of the respective liquid crystal cells C are respectively aligned in the vertical and horizontal directions as shown by broken lines in the figure.
Accordingly, as a method for disposing the color filters relative to the aligned picture elements (electrodes P), there is frequently employed a color filter of a so-called stripe type as shown in FIG. 14. In the figure, reference letter R represents a red color filter, G a green color filter and B represents a blue color filter.
However, in the case of such stripe-type color filter, the resolution in the horizontal direction is lowered to 1/3 as compared with a monochromatic type so that the quality of a picture is deteriotated considerably.
While, a color filter of a so-called mosaic type is proposed as shown in FIG. 15, in this case, although the horizontal resolution is improved as compared with the stripe-type color filter, as will be clear from the figure, the color filters having the same color are disposed obliquely so that slant color lines like a beat interference appear in the picture, thus the quality of the picture being deteriorated considerably.